Experimental Analysis of the Interaction Between a Dual-Bell Nozzle with an External Flow Field Aft of a Backward-Facing Step

Bolgar, Istvan; Scharnowski, Sven; Kähler, Christian J.

doi:10.1007/978-3-030-25253-3_39

Cited by 5 publications

(12 citation statements)

References 16 publications

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“…Thus, it is important to keep in mind that some of the results could be caused by the planar geometry of the model. The nozzle's thrust chamber is fed by two hoses (2-inch diameter), one on either side of the model [9]. To control the nozzle flow state, the total pressure in the nozzle settling chamber p 0,nozzle as well as the static pressure in the outer flow p ∞ can be adjusted.…”

Section: Measurement Set-upmentioning

confidence: 99%

“…It is important to note that the mode transition NPR is shifted towards smaller values with the outer flow turned on. This change in mode transition NPR is caused by the aspiration drag [20] which causes a reduction of the static pressure near the nozzle exit relative to the freestream, as shown in [9]. The standard deviation of the schlieren intensity in Fig.…”

Section: Schlieren Statisticsmentioning

confidence: 99%

“…The jet is operated in altitude mode already at NPR= 3.7 . The reason for the nozzle mode transition at much lower NPR values compared to subsonic condition is the massively reduced static pressure due to flow expansion around the nozzle's lip [9].…”

Section: Schlieren Statisticsmentioning

confidence: 99%

“…This leads to a recirculation region at the nozzle outlet and inside the second bell, which in combination with the external flow can cause additional instabilities. In [9], it was shown that with supersonic outer flow, the expansion around the nozzle's lip causes premature switching to altitude mode which is not yet stable, resulting in multiple transitions and re-transitions between both nozzle modes. Consequently, the transition to altitude mode should be completed before the sound barrier is crossed, with this kind of space launcher geometry.…”

Section: Introductionmentioning

confidence: 99%

“…The focus here is on the sea-level mode in subsonic outer flow, because in altitude mode, the dual-bell nozzle performs like a single bell nozzle with TIC or TOC contour. The sea-level mode with supersonic outer flow is less relevant because the mode transition should take place in subsonic outer flow for safety and efficiency reasons [9,46]. The model, the test facility and the experimental approaches are described in Sect.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the base flow of a generic space launcher with dual-bell nozzle

Scharnowski

Kähler

2020

CEAS Space J

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The typical afterbody flow of a space launcher is characterized by a strong interaction of the engine’s exhaust jet and the separated shear layer emerging from the main body. This interaction is further complicated by strong changes in the spatial and temporal behavior of the afterbody flow during the atmospheric ascent of a launcher. Theoretically, a dual-bell nozzle not only allows for a gain in payload compared to standard single-bell nozzles, but also it alters the wake flow topology due to the two nozzle modes. To predict the benefits as well as the additional risks, the afterbody flow of a generic space launcher model equipped with a cold-flow dual-bell nozzle is investigated in detail. The flow was analyzed for sub-, trans- and supersonic Mach numbers ranging from 0.3 to 2.9 for a variety of nozzle pressure ratios. Particle image velocimetry measurements and schlieren measurements with high repetition rate were performed to determine the dynamics of the separated shear layer, the nozzle jet and their interaction. It is shown that the reattachment length of the base flow decreases with increasing nozzle pressure ratio. Furthermore, the nozzle pressure ratio at which the dual-bell nozzle switches from sea-level mode to altitude mode is reduced by $$15\%$$ 15 % with high subsonic outer flow and by as much as $$65\%$$ 65 % for an outer flow at a Mach number of 1.6. Even for a constant nozzle pressure ratio, the nozzle flow topology depends on the Mach number of the outer flow.

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Section: Measurement Set-upmentioning

confidence: 99%

Section: Schlieren Statisticsmentioning

confidence: 99%

Section: Schlieren Statisticsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Investigation of the base flow of a generic space launcher with dual-bell nozzle

Scharnowski

Kähler

2020

CEAS Space J

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Effects of a Launcher’s External Flow on a Dual-Bell Nozzle Flow

Bolgar

Scharnowski

Kähler

2020

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Previous research on Dual-Bell nozzle flow always neglected the influence of the outer flow on the nozzle flow and its transition from sea level to altitude mode. Therefore, experimental measurements on a Dual-Bell nozzle with trans- and supersonic external flows about a launcher-like forebody were carried out in the Trisonic Wind Tunnel Munich with particle image velocimetry, static pressure measurements and the schlieren technique. A strongly correlated interaction exists between a transonic external flow with the nozzle flow in its sea level mode. At supersonic external flow conditions, a Prandtl–Meyer expansion about the nozzle’s lip decreases the pressure in the vicinity of the nozzle exit by about 55%. Therefore a new definition for the important design criterion of the nozzle pressure ratio was suggested, which considers this drastic pressure drop. Experiments during transitioning of the nozzle from sea level to altitude mode show that an interaction about the nozzle’s lip causes an inherently unstable nozzle state at supersonic free-stream conditions. This instability causes the nozzle to transition and retransition, or flip-flop, between its two modes. This instability can be eliminated by designing a Dual-Bell nozzle to transition during sub-/transonic external flow conditions.

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Interaction of Wake and Propulsive Jet Flow of a Generic Space Launcher

Barklage

Radespiel

2020

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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This work investigates the interaction of the afterbody flow with the propulsive jet flow on a generic space launcher equipped with two alternative nozzle concepts and different afterbody geometries. The flow phenomena are characterized by experimental measurements and numerical URANS and LES simulations. Investigations concern a configuration with a conventional truncated ideal contour nozzle and a configuration with an unconventional dual-bell nozzle. In order to attenuate the dynamic loads on the nozzle fairing, passive flow control devices at the base of the launcher main body are investigated on the configuration with TIC nozzle. The nozzle Reynolds number and the afterbody geometry are varied for the configuration with dual-bell nozzle. The results for integrated nozzles show a shift of the nozzle pressure ratio for transition from sea-level to altitude mode to significant lower levels. The afterbody geometry is varied including a reattaching and non-reattaching outer flow on the nozzle fairing. Investigations are performed at supersonic outer flow conditions with a Mach number of $$Ma_\infty =3$$. It turns out, that a reattachment of the outer flow on the nozzle fairing leads to an unstable nozzle operation.

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Experimental Analysis of the Interaction Between a Dual-Bell Nozzle with an External Flow Field Aft of a Backward-Facing Step

Cited by 5 publications

References 16 publications

Investigation of the base flow of a generic space launcher with dual-bell nozzle

Investigation of the base flow of a generic space launcher with dual-bell nozzle

Effects of a Launcher’s External Flow on a Dual-Bell Nozzle Flow

Interaction of Wake and Propulsive Jet Flow of a Generic Space Launcher

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